The goal of this research project proposal is to investigate a novel combination therapy for KRAS-driven non-small cell lung cancer (NSCLC) that involves inhibition of pro-tumorigenic cytokine production. Work from this laboratory identified the JAK kinase inhibitor CYT387 (momelotinib) as a potent inhibitor of the immune signaling kinases TBK1/IKK?, disrupting a cytokine circuit that oncogenic RAS engages to promote tumor cell survival and migration. Although efficacious as single agent therapy in Kras-driven murine lung cancer, combination pathway inhibition with a MEK inhibitor resulted in synergy and prolonged tumor regression in an aggressive mouse model of Kras-p53 driven lung cancer. The broad, long term objective is to perform research at the bench to bedside interface to explore further the mechanistic basis that underlies the synergy of this combination therapy, and to identify additional strategies to enhance response and overcome resistance. A unique aspect of this proposal is that it spans basic and translational research and incorporates analysis of an actual clinical trial impacting patients. Specific aims are to: 1) Explore synergy and resistance to TBK1 and MEK inhibition in murine Kras-driven lung cancer through further genetic and pharmacologic studies. 2) Elucidate the molecular circuitry responsible for TBK1/MEK inhibitor synergy, and 3) Evaluate response and resistance to momelotinib/trametinib combination therapy in a phase 1b/2 clinical trial in human KRAS mutant NSCLC. The use of mouse lung cancer models will facilitate pharmacogenetic and pharmacodynamics studies that will define the specific activities of the momelotinib/trametinib combination. Genetic crosses of conditional TBK1 null or kinase dead mice into the oncogenic Kras-driven lung cancer model, together with selective JAK and MEK inhibitor treatment, will identify the unique role of TBK1 in regulating this autocrine cytokine circuit in vivo. Analysis of momelotinib/trametinib efficacy across Kras, Kras-p53, and Kras-Lkb1 murine lung cancer models will determine genetic modifiers of response and de novo resistance. Further investigation of TBK1 signaling in KRAS-dependent human cancer cell lines in vitro will elucidate the mechanism by which its inhibition leads to feedback activation of MEK-ERK signaling, yielding important biologic insights and a better understanding of TBK1/MEK inhibitor synergy. Finally, the determination of resistance mechanisms that develop in mouse models and in patients will further define the key activities of these inhibitors. Through these complementary studies, the ultimate goal is not only to understand mechanism and target this therapy to the appropriate subgroup of patients, but also to identify additional strategies for combination therapy that leads to durable control of this aggressive disease.